The accumulation and activation of CD4+ T cells in the synovial membrane are central events in the pathogenesis of rheumatoid arthritis (RA). Mechanisms whereby inflammatory cells are recruited to the tissue as well as the mechanisms whereby such cells are stimulated to damage tissue are not understood. We have isolated CD4+ Vbeta3+ or Vbeta17y+ T cell clones with identical beta chain sequences from the peripheral blood and the synovial fluid of two patients with early and aggressive disease. Analysis of Vbeta-Jbeta combinations in five additional RA patients revealed that the repertoire of Vbeta3+, but not Vbeta1+, CD4+ T cells was majorly skewed. While clonal expansion of selected T cell specificities supports the model of an antigen-driven process, the extent of the repertoire shift raises the possibility that Vbeta specific activation precedes selection of individual T cells. The hypothesis being addressed by this proposal is that an acute event, i.e., an infection with a microorganism harboring a superantigen, precedes the onset of RA, and induces a shift in the repertoire of Vbeta3+ and Vbeta17+ T cells. In this model, oligoclonal expansion would result from the selection of Vbeta3+ and Vbeta17+ T cell clonotypes which may either be specific or microbial products or for autoantigens. We propose to extend our studies on the T cell receptor (TCR) diversity of CD4+ Vbeta3+ and Vbeta17+ T cells by analyzing Vbeta-Jbeta combinations and sequencing overrepresented specificities in early RA patients. Vbeta specific reagents will be used to enrich for CD4+ Vbeta3+ and Vbeta17+ T cells. To mycoplasma derived superantigen MAM specifically activates Vbeta17+ T cells, raising the interesting possibility that repertoire abnormalities in RA patients could result from a previous encounter with a microbial product. We will subsequently test the hypothesis that an acute event in early RA has resulted in a permanent imprint on the TCR repertoire of patients with established RA. We have collected a series of families with multiple affected members and are proposing to compare TCR diversity of CD4+ Vbeta3+ or Vbeta17+ T cells in patients and nonaffected relatives. Finally, the availability of T cell clones opens the possibility to define disease relevant antigens. We will study the specificities of Vbeta3+ and Vbeta17+ T cell clones representative of clonally expanded populations. Utilizing antigen specific recognition by such T cell clones, we will identify the tissue harboring such antigens in the joint and attempt to isolate and characterize antigenic peptides driving the proliferation of clonally expanded T cell specificities.